wrap mortgage - how would you structure this?

[Craig M]

I'm thinking of selling my personal residence on a wrap, but I wanted to see what you thought about these approximate numbers (rounded for simplicity):

$140k sales price
$30k down payment from buyer

$95k owed on my existing mortgage @ 4.875%
$550 P&I monthly payment ($650 w/ taxes and insurance)

Seller finance the $110k left w/ a wrap w/ a 3 year balloon.

How would you structure the deal in regards to interest rate to the buyer. I've heard add 1-2% to your current rate, but it seems I could do a little more than that and it still be an attractive deal for the buyer.

Also, I would like to find a loan processing company to deal w/ the payments & record keeping. What is a fair price to pay for those services?

(And I know a wrap probably isn't the first option many would choose, but I'm in Texas so its really my only option)